The spinal disc is the natural shock absorber located between all vertebrae. In the event it becomes traumatized through injury or degenerates through age or disease, the intervertebral space is reduced through compression and the relative movement of adjacent vertebrae causes pain. The surgical approach to this problem is to relieve the compression, stabilize the adjacent vertebrae and provide for a natural fusing of the vertebrae into one unit.
There are many spinal implants used to stabilize two adjacent vertebrae to prevent relative movement until the vertebrae are fused together by boney ingrowth through and around the implant. Generally these implants are in three groups, i.e., bone plates, pedicle screw/rod constructs and spinal cages. The bone plates span the intervertebral space and are affixed to the two adjacent vertebrae anteriorly by bone screws. Pedicle screw/rod constructs span the vertebral bodies posteriorly and are often connected with cross-links.
The spinal cages are inserted between the adjacent vertebrae and are usually seated into to the end plates of the adjacent vertebrae. To gain access to the intervertebral space, a site is prepared by removing a portion or all of the spinal disc. A wedge shaped distractor is inserted into the site to gradually separate the adjacent vertebrae until the desired intervertebral space is achieved and cut into the end plates of the adjacent vertebrae. Once the site is prepared, the distractor is removed and the spinal implant is inserted into the disc space. The spinal implant may be packed with bone growth material, bone chips, a combination of both, or other material. The implant usually has openings to allow boney ingrowth to occur. One such device is taught by Liu et al, U.S. Pat. No. 6,746,484 B1.
What is needed in the art is a less complex spinal implant methodology using fewer instruments to reduce surgical time and resulting in a more secure union between the implant and the spine.